The expensive, uncertain, yet talented central defensive combination of Eliaquim Mangala and Nicolas Otamendi clearly needs longer to adjust to the demands of English football. In that context, City manager Manuel Pellegrini must have been concerned about the potential impact of Troy Deeney and Odion Ighalo.

Both Watford strikers have thrived this season through employing physical tactics - and against more experienced opposition - and it would have come as little surprise had they again targeted City's inconsistent defence.

As early as the second minute Deeney showed his confidence with a run that led to Almen Abdi sending a promising 25-yard shot both high and wide, and shortly after Ighalo first encountered the £32million Otamendi.

In this instance the Argentinian defender impressed when, with Ighalo in space in the area following Abdi's through-ball, he read the striker's shot to lunge and deflect it out for a corner.

Ighalo swiftly threatened, again having been played in by Abdi - but when he produced a nice turn to beat Otamendi, City goalkeeper Joe Hart reacted to rush out, dive, and smother his shot clear.

City's response came through strikes from Kevin de Bruyne and Fernandinho, both of which Watford's Heurelho Gomes comfortably saved, but beyond Aguero's runs and a 25-yard, swerving shot from Kolarov which went just high and wide of the left angle, they rarely looked like scoring throughout the first half.

Watford similarly began the second half with greater promise.

There would have been a time when, particularly while comparing their resources with City's, 0-0 would have been an encouraging scoreline but manager Quique Sanchez Flores has quickly organised them into a strong team that has little reason to be intimidated.

A powerful header just over the crossbar from Fernandinho served as a reminder of the quality City possess and how quickly they are capable of changing a game, but almost immediately after - in a demonstration of why that quality alone cannot always be relied upon - Watford took the lead.

Taking an inswinging corner from the left, Ben Watson's accurate delivery troubled City's defence, evading everyone except for Kolarov, whose header served to help it into the back of the net. It was recorded as an own goal, even if it was already going in, and again highlighted the damage caused by the absence of City's authoritative captain, Vincent Kompany.

Toure, so often decisive, soon struck beyond the crossbar from the edge of the area, and Kevin De Bruyne forced a routine save from Gomes - but Watford's discipline meant only a moment of quality looked likely to rescue them, and so it ultimately proved.

The midfielder has this season occasionally looked in decline, but when Kolarov sent in an 82nd-minute corner from the left, Toure casually and classily volleyed into the top left corner to equalise.

Their winning goal came just two minutes later. From space on the right wing, Bacary Sagna curled a superb cross towards Aguero, and under little pressure the forward headed beyond Gomes and into the back of the net, improving City's title prospects in the process.

TWEET OF THE MATCH

@RodneyMarsh10: "Harsh on Watford but that's what happens when you have world class footballers."

PLAYER RATINGS

Watford

Heurelho Gomes: 7

Allan Nyom: 6

Miguel Britos: 7

Craig Cathcart: 7

Jose Holebas: 6

Almen Abdi: 7

Etienne Capoue: 7

Ben Watson: 7

Jose Manuel Jurado: 7

Troy Deeney: 7

Odion Ighalo: 7

Subs

Adlene Guedioura: 5

Manchester City

Joe Hart: 6

Bacary Sagna: 7

Nicolas Otamendi: 6

Eliaquim Mangala: 6

Aleksandar Kolarov: 7

Fernandinho: 6

Yaya Toure: 8

Kevin de Bruyne: 6

David Silva: 6

Raheem Sterling: 5

Sergio Aguero: 7

Subs

Jesus Navas: 6

Wilfred Bony: 6

Martin Demichelis: 5

STAR PLAYER

Yaya Toure. He may no longer be capable of exerting the same consistent influence that has long been crucial to City, but he retains the ability to produce moments of quality that could yet define their season. His goal came from nowhere, but was exceptional, and ultimately changed the game.

MOMENT OF THE MATCH

In the first half, Jose Manuel Jurado chipped a masterful, scooped pass when under pressure with little space on the left wing. It was a delightful moment of quality and spontaneity, and showed why he may just be Watford's most naturally-talented player since John Barnes - Ashley Young included.

VIEW FROM THE BENCH

Manuel Pellegrini's overriding emotion at victory is likely to be relief. His City team, rather inexplicably given their exceptional quality, continue to disappoint, and he will know they only won because of that quality, and not through any substitutions he made. Watford's Quique Sanchez Flores will know his team deserved better. Their organisation showed throughout, and but for two fine players they would have earned a good draw, if not an outstanding win.

MOAN OF THE MATCH

Raheem Sterling's performance. His £49million summer transfer to City from Liverpool was supposed to inspire him to a greater level, and help inspire City to further success. He, and City, look little better than last season. Surrounded by such quality, he should be thriving, but he looked disinterested and frustrated, and was substituted on the hour mark.

WHO'S UP NEXT?

Watford v Newcastle (FA Cup, Saturday, January 9).

Everton v Manchester City (Capital One Cup, Wednesday, January 6).

City boss Manuel Pellegrini told Sky Sports 1: "I've always said this team has character, we never give up.

"I think tonight we were unlucky to be losing the game. It wasn't a corner and then it was an own goal.

"But we kept our minds and made some changes, always thinking we are able to turn the corner - and we did.

"It was a very close game and tough for both teams but if you see the statistics we deserved to win, we had more shots on target and possession."

On Aguero's goal, his first since returning from injury, the Chilean added: "A goal is important for a striker and he had better movement than the last game.

"We are not sending messages to anyone - we go game by game and we must stay focused."

City goalkeeper Joe Hart said: "I know we're capable of doing that but the Stoke game and this one gave me a bad feeling when I'm in goal. I was hoping and praying we would put it together and we did.

"Six on the road without a win is not championship-winning form ... but we've got all the big boys to come to us and big cup games coming up, which our focus now turns to.